Rule 310 and 408 - ACE and OCF channels should be able to have an empty response

[rcasey-earthscope]

We want to address these warnings relating to ACE and OCF channels as they apply only to channels with a sample rate and response. ACE and OCF can have an empty response block.

• 310 : ACE : Sample rate cannot be 0 or null.
• 310 : ACE : Sample rate cannot be 0 or null.
• 312 : ACE : expected a value for calibration unit but was null
• 312 : ACE : expected a value for calibration unit but was null
• 408 : ACE : Decimation cannot be null
• 408 : ACE : Decimation cannot be null

[rcasey-earthscope]

Also see rule #22 and rule #24 as they are addressing essentially the same issue.

[timronan]

Error 310 has been corrected to allow SOH, ACE, OCF channels to have a sample rate of 0. Error 310 checks only for sample rates, it does not verify that a channel's metadata contains a response that includes B053-B056, B057, B058.

Error 312 was adjusted to allow a null calibration unit.

Error 408 has been adjusted to allow for the Decimation blockette, B057, to be null for channels that are assigned as SOH, ACE, OCF.

SOH, ACE, OCF can have an empty response, a sample rate of zero and can pass the current version of the validator.

Refer to: https://service.iris.edu/fdsnws/station/1/query?net=AK&cha=OCF&starttime=2018-06-01T00:00:00&level=response&format=xml&includecomments=true&nodata=404, which passes validation.